The four, identified as Lebanese Fadi Munir Yasin, Charbal Karam Haj and Aram Nalbandian and Iraqi Ahmad Mirza, were seized by armed men on the Baghdad-to-Falluja highway on Friday night, a Foreign Ministry official said.
On Sunday the official, speaking on condition of anonymity, said the three Lebanese worked for a travel agency that has a branch in Baghdad.
The motive for the abduction was not made clear.
Friday's incident came a week after armed men killed three Lebanese who worked for a food company in Baghdad and wounded a fourth in one of the victim's homes. The victims included a man and his wife.
The circumstances surrounding the deaths were unclear.
Shukri Nmir, who was wounded in the 10 September shooting, said the men who raided their house were disguised as police officers and that the attack might have been an attempted kidnapping gone wrong.
About 120 foreigners have been taken captive in Iraq, and many have been killed by their captors.
Lebanese are threatened if they
continue to work with US army
Armed attackers have carried out most of the abductions in an attempt to drive foreign companies out of Iraq and defeat the US-led forces in the country.
Several Lebanese business people and truck drivers have been captured in Baghdad in recent months. All were released unharmed except for one.
Husain Ali Alyan, a 26-year-old Lebanese construction worker, was found shot dead on 12 June. Foreign Ministry officials have said Alyan's captors sought ransom and were apparently not politically motivated.
Hundreds of Lebanese, mainly construction workers and industrialists, have gone to Iraq to look for opportunities in the massive postwar reconstruction.
On Thursday, a website statement signed by an armed Iraqi group - purported to have briefly held a Lebanese-American US Marine last June - threatened to "slaughter any Lebanese working with the US Army and drag their bodies through the streets of Iraq".